Real-Time Clock (Rtc) And Non-Volatile Memory (Nvm) - HP 9030 Service Manual

Testing and Troubleshooting
3-19
Real-Time Clock (RTC) and Non-Volatile Memory (NVM)
The system control module contains the RTC and NVM chips and the battery assembly to maintain
data in both chips during power-off states.
The RTC and NVM chips store a clock, system configuration data, and service information of
significance to users and service personnel. The clock is initially loaded from the lOP and is updated
by a crystal oscillator. The RTC chip stores clock and calendar data in 16 four-bit locations; the
NVM chip has 2048 eight-bit locations and stores service and configuration data. RTC/NVM
locations and contents are as follows:
Byte 0 - Second
Byte 1 - Clock Check Byte
Byte 2 - Minute
Byte 3 - Stack Size (two times number of finstrates)
Byte 4 -Hour
Byte 5 - Century
Byte 6 - Day of Week
Byte 7 - Day of Month
Byte 8 - Month
Byte 9 - Year
Bytes 10-13 - Control Registers
Byte 14 - Timer Resolution
Byte 15 - Timeout Scan Resolution
Byte 16 - Keyboard Initialization Data
Bytes 17-24 - Default System Startup Subsystem
Bytes 25-44 - Default Mass Storage Unit Specifier (MSUS)
Byte 45 - Size of System
110
Buffer
Bytes 46-47 - NVM Checksum
Bytes 48-53 - Healer CAM Overflow Counter
Bytes 54-57 - Last Double Bit Memory Failure Data
Bytes 58-60 - Number of 10-Minute Periods Computer is On
Byte 61 - Number of Overheat Cycles
Bytes 62-63 - Number of Power-On Cycles
The system control module contains a nickel-cadmium battery assembly consisting of four batteries
to maintain the RTC and NVM chips during a power-off condition. Because only three batteries are
required, one is redundant. This enables the chips to operate without error if one of the batteries
has a short circuit. The battery assembly maintain RTC and NVM data for a minimum of 10 days
while power is off.